The present invention relates to sewing machines which include a thread take-up lever and a thread take-up member disposed on a portion of an upper thread path immediately upstream of the thread take-up lever, and more particularly to a sewing machine improved to facilitate setting of an upper thread onto a thread take-up member disposed upstream of a thread take-up lever.
Chinese Patent Application Publication No. CN102140742 (hereinafter referred to as “the relevant patent literature”) discloses a multi-needle embroidery sewing machine which includes a thread take-up member disposed on a portion of an upper thread path immediately upstream of a thread take-up lever and which facilitates setting of an upper thread onto the thread take-up member. The embroidery sewing machine disclosed in the relevant patent literature includes a thread take-up lever cover integrally covering a plurality of thread take-up levers in a predetermined range of a vertical (or up-down) pivoting path of the thread take-up levers. The thread take-up lever cover comprises a bottom plate and a forwardly-bulging panel, and slits are formed in the forwardly-bulging panel in corresponding relation to the thread take-up levers. An upper portion and lower portion of each of the slits each have an increased width, and a distal end portion of the thread take-up lever is inserted in the upper portion of the slit while a later-described holding plate cover is inserted in the lower portion of the slit. A fixing plate is fixed in the interior of the thread take-up lever cover by being inserted from the back side of the thread take-up lever cover, and thread take-up members are provided on the fixing plate in corresponding relation to the thread take-up levers. Each of the thread take-up members includes a holding plate fixed to the front surface of the fixing plate, the holding plate cover fixed to the front end of the holding plate, and each of the holding plate covers is inserted in the lower portion of the corresponding slit and has a lower end portion projecting forward beyond the panel. A thread tension device is provided on one side surface of the holding plate. The thread tension device includes a disk and a pin, the disk is mounted to the holding plate via the pin, and the disk has a plurality of holes formed in the disk along a same imaginary circle of the disk. The thread tension device includes a thread take-up spring that has a coiled spring section fitted over the pin and a forwardly-projecting thread take-up hook section of a triangular shape. The proximal end of the coiled spring section of the thread take-up spring is inserted in any one of the plurality of holes formed in the disk. Further, the holding plate has a recessed groove of an arcuate shape corresponding to a movement trajectory of the thread take-up hook section of the thread take-up spring, and the thread take-up hook section is positioned in the recessed groove.
When a thread is to be set onto the thread take-up member and the thread take-up lever in the embroidery sewing machine disclosed in the relevant patent literature, the thread is passed through the corresponding slit formed in the panel, then directed from the right side of the holding plate cover to and across the lower side, located in front of the panel, of the holding plate cover, then turned back and then pulled upward. Thus, the thread is directed along the recessed groove of the holding plate into the triangular thread take-up hook section of the thread take-up spring. Then, the thread is passed through the thread take-up lever, turned back downward, then passed through the slit and directed along the left side of the holding plate cover to a sewing needle. Thus, according to the embroidery sewing machine disclosed in the relevant patent literature, setting of a thread onto the thread take-up member can be performed with ease. Besides, because of the arrangements that the disk of the thread take-up device has the plurality of holes formed along the same imaginary circle of the disk and the proximal end of the coiled spring section of the thread take-up spring is insertable in any one of the plurality of holes, spring resilience of the thread take-up spring is adjustable by changing the hole where the proximal end of the coiled spring section is inserted to another one of the holes. In this way, spring resilience suited for any desired threads to be used can be obtained.
When maintenance is to be performed on the thread take-up lever in the embroidery sewing machine disclosed in the relevant patent literature, it is necessary to dismount or detach, from the machine head, the thread take-up lever cover having the thread take-up member fixed thereto and then detach, from the back surface side of the thread take-up lever cover, the fixing plate having the thread take-up member fixed thereto. Thus, in order to detach the thread take-up lever cover, all threads set on the sewing machine have to be removed. Thus, when the thread take-up lever cover is mounted or attached again, all of the threads have to be set again. For these reasons, operations involved in the maintenance tend to be very bothersome and time-consuming.
Further, when the hole of the disk in which the proximal end of the coiled spring section of the thread take-up spring is inserted is to be changed to another one of the holes, it is necessary to further detach the holding plate from the fixing plate and detach the disk from the holding plate. This is because, with the holding plate left fixed to the fixing plate, the disk cannot be detached due to interference between the holding plate and other holding plates adjoining that holding plate. Thus, the operation for changing the spring resilience too tends to be very bothersome and time-consuming. Namely, with the embroidery sewing machine disclosed in the relevant patent literature, the operations involved in the maintenance have been very laborious and time-consuming.